Whole Blood Leukocyte Mitogen Activated Protein Kinases Activation Differentiates Intensive Care Unit Patients With Systemic Inflammatory Response Syndrome and Sepsis

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Abstract
Introduction: We sought to determine whether leukocytes from intensive care unit (ICU) patients have altered ERK and p38 kinase activation and specifically if septic patients manifest changes of endotoxin (lipopolysaccharide [LPS]) tolerance. In vitro pretreatment of monocytes (Mono) with LPS induces LPS tolerance with impaired cytokine release and inhibition of ERK and p38 activation after LPS rechallenge. Hypothesis: We hypothesized that macrophage dysregulation, similar to that seen with in vitro LPS tolerance, occurs in critically ill patients with severe sepsis. Methods: Heparinized whole blood from 16 surgical ICU patients and 16 healthy controls was incubated for 15 minutes ± 10 ng/mL LPS at 37°C. Mono and neutrophil (polymorphonuclear leukocytes [PMN]) diphospho (active) ERK and p38 kinase activation were determined using flow cytometry with monoclonal antibodies. Results are expressed as mean ± SEM of basal and percentage change (delta %) in positive cells (delta = LPS stimulated − basal). χ2 test was used for statistics. Results: Basal ERK was seen in Mono from all groups, but delta % positive only increased in healthy subjects and systemic inflammatory response syndrome (SIRS) patients. No basal Mono or PMN p38 was seen in healthy controls, but LPS significantly activated p38 in both cell types. Mono from patients with sepsis, but not SIRS, had impaired ERK activation. Both PMN and Mono from patients with SIRS had low basal but high LPS-stimulated p38, whereas p38 activation was impaired in patients with sepsis. Conclusion: Alterations in mitogen activated protein kinases (MAPK) activation are seen in ICU patients. Leukocytes of septic patients, but not those with SIRS, showed characteristics of LPS tolerance. Assessment of leukocyte MAPK activation may identify and differentiate patients with sepsis from those with SIRS.